In recent years, a technique for improving fuel efficiency by automatically stopping an engine at the time of stopping a vehicle (i.e., an idle stop control) is well known.
For example, in the case of a delivery truck, a driver stops a vehicle during delivery of cargos, gets off a driver seat, accesses a carrier so as to take out a cargo to be delivered. The driver performs the above actions frequently. For this reason, a technique for linking an idle stop control with an air suspension vehicle height adjustment is disclosed (e.g., see Patent Literature 1).
Also, in order to command the engine to stop by the idle stop control, the vehicle should be at a requesting stop step of the engine, and should not under a predetermined operation condition which prevents the engine from being stopped. As an example of the predetermined operation condition which prevents the engine from being stopped, a parking operation can be cited. A technique which uses the parking operation as the predetermined operation condition so that a stop command is not issued to the engine by the idle stop control is disclosed (e.g., see Patent Literature 2).
By the way, in a vehicle which has an idle stop control device using a self-starter and does not have a power source backup of an electric power steering device (hereinafter, referred to as an “EPS”), a large current flowing through a motor for the self-starter causes a battery voltage to drop at the time of cranking.
FIG. 6 shows a power source voltage drop at the start time of cranking. When the cranking is started, a power source voltage VEPS of an unit terminal of the EPS changes as shown by a bold solid line in FIG. 6. Also, as shown by a broken line in FIG. 6, the voltage further drops if the battery deteriorates.
A normal EPS becomes difficult to perform an assist compensation at a voltage equal to or less than about 10V. Also, at a voltage equal to or less than 7V, a CPU reset occurs. Within a area A shown in FIG. 6, the EPS can not perform assist (EPS assist OFF).
For this reason, if the EPS performs the assist, when an engine starting (a cranking) occurs, a steering (hereinafter, referred to as a “handle”) is turned back by an instantaneous assist OFF (area A) and a large reaction force (a kickback) is applied to an user.
As described above, if the vehicle does not have the power source backup of the EPS, for example, the EPS assist may be stopped at the time of cranking in order to relieve the reaction force of the handle. That is, if the EPS assist is stopped in advance, the handle reaction force does not occur.
FIG. 7 shows an example of control of an idle stop state and an EPS assist for relieving the handle reaction force. As shown in FIG. 7, if a vehicle is stopped, only when a steering speed caused by a user's operation becomes small, the state transits to an idle stop state and the EPS assist is turned OFF at the same time. After that, when the engine performs complete explosion, the EPS assist is turned back (EPS assist ON).